A second Iowa producer recalls 170 million eggs shipped to 14 states as long ago as April after tests show possible salmonella contamination.

In another blow to the nation's $6-billion egg industry, a second Iowa producer issued a recall of 170 million eggs that could be contaminated with salmonella — bringing the total number to more than half a billion.

The eggs were produced by Hillandale Farms of New Hampton, Iowa, and packaged under at least five brands and had been shipped to 14 states, including California.

The company said in a statement Friday that laboratory tests of its eggs from two of its plants had confirmed some illnesses and that the eggs "have the potential to be contaminated with salmonella."

The producer said that the eggs were produced and packaged as early as April 10 until as recently as Thursday. The federal Food and Drug Administration said it was investigating the circumstances of the latest recall.

This marks the second time this week that a large Iowa producer has recalled eggs due to concerns over Salmonella enteritidis. Earlier this week, Wright County Egg of Galt, Iowa, expanded its recall to 380 million eggs, which federal public health officials believed may be linked to 1,000 or more salmonella infection cases nationwide.

"I don't know what's caused this current situation, or what the tie is between the outbreaks in these two farms, but we need to find out," said Howard Magwire, a vice president of the national trade group United Egg Producers.

Late Friday, Cal-Maine Foods Inc., the nation's largest egg seller and distributor, said it was recalling about 9.6 million eggs related to this week's recalls, the Associated Press reported. It wasn't immediately clear which Iowa producer supplied the Cal-Maine eggs.

The eggs recalled by Hillandale Farms were sold under the farm's own name and the brand names Sunny Farms, Sunny Meadow, Wholesome Farms and West Creek and were distributed to grocery wholesalers, retail grocery outlets and food service companies in California, Arkansas, Iowa, Illinois, Indiana, Kansas, Minnesota, Missouri, Nebraska, North Dakota, Ohio, South Dakota, Texas, and Wisconsin, the company said in a statement.

The eggs were packaged in six-, dozen-, 18- and 30-egg cartons, and in cases of five dozen, the company said. Other eggs were packaged in 15- and 30-dozen tray packs.

The company said that consumers who bought these brands should check the egg cartons for two key identifying stamps. One is the number of the plant in which the eggs were produced — P1860 or P1663. The second is the so-called Julian or packing date codes — in this case, ranging from 099 to 230 for cartons with a plant number of 1860, and from 137 to 230 for cartons with a plant number of 1663.

On Thursday, federal officials warned that the number of cases of people sickened by contaminated eggs will probably grow amid the recall, one of the largest of its kind in recent history. The salmonella outbreak occurred as new FDA egg-safety rules came into effect in early July, which require producers to do more testing for salmonella and take other precautions. The rule is intended to reduce the risk of salmonella infections in eggs.

A spokeswoman for Wright County Egg said this week that the company was in compliance with the rule when it officially went into effect on July 9. She declined to say whether the firm was following the guidelines on July 8 or earlier. Industry officials on Friday said that egg producers in California and elsewhere had begun implementing these measures months ago.

"Everyone has known that these rules were coming and started adapting to them," said Debbie Murdock, executive director of the Assn. of California Egg Farmers.

This week, FDA officials said that the new rules could have helped prevent the salmonella outbreak: From May through July, 1,953 salmonella cases were reported, officials with the Centers for Disease Control and Prevention said. That number — compared with the average 700 cases reported in the same time frame of the last five years — alerted federal officials to the seriousness of the outbreak.

But Magwire pointed out that the FDA hadn't done any inspections at either Hillandale Farms or Wright County Egg plants, as the agency is still in the process of training inspectors.

There have been financial ties between the people who own and operate Wright County Egg and Hillandale Farms.

Wright County Egg is headed up by Austin "Jack" DeCoster, whose Galt, Iowa, operation is where the initial 380 million recalled eggs were produced.

In 2003, DeCoster made a $125-million investment in Ohio Fresh Eggs — a company co-owned by Orland Bethel, who is also the owner of Hillandale Farms. Ohio state officials questioned the investment, but a state court ultimately ruled there was no wrongdoing.

An Ohio Agriculture Department spokesman said Friday that DeCoster was still an investor in Ohio Fresh Eggs. DeCoster did not return calls for comment.

Calls to Bethel's offices in North Versailles, Pa., and in Iowa were not returned.